Method and device for determining a concentration of at least one analyte

ABSTRACT

A method for determining a concentration of at least one analyte in bodily fluid, comprising: a signal generation step, wherein an excitation voltage signal is generated by a signal generator, wherein the excitation voltage signal comprises a poly frequent alternating current (AC) voltage and a direct current (DC) voltage profile, wherein the poly frequent AC voltage comprises at least two frequencies; a signal application step, wherein the excitation voltage signal is applied to at least two measurement electrodes; a measurement step, wherein a response is measured by using the measurement electrodes; an evaluation step, wherein an AC current response for each frequency and a DC current response are evaluated from the response; a determination step, wherein the concentration of the analyte is determined from the DC current response and from one or both of the phase and impedance information by using at least one predetermined relationship.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/EP2017/083838, filed 20 Dec. 2017, which claims the benefit ofEuropean Patent Application No. 16205825.9, filed 21 Dec. 2016, thedisclosures of which are hereby incorporated herein by reference intheir entirety.

TECHNICAL FIELD

The present disclosure relates to methods and devices for determining aconcentration of at least one analyte. The method and devices accordingto the present disclosure may be used for detecting at least one analytepresent in one or both of a body tissue or a body fluid, in particularthe method and devices are applied in the field of detecting one or moreanalytes such as glucose, lactate, triglycerides, cholesterol or otheranalytes, typically metabolites, in body fluids such as blood, typicallywhole blood, plasma, serum, urine, saliva, interstitial fluid or otherbody fluids, both in the field of professional diagnostics and in thefield of home monitoring. However, other fields of application arefeasible.

BACKGROUND

In the field of medical technology and diagnostics, a large number ofdevices and methods for detecting at least one analyte in a body fluidare known. The method and devices may be used for detecting at least oneanalyte present in one or both of a body tissue or a body fluid, inparticular one or more analytes such as glucose, lactate, triglycerides,cholesterol or other analytes, typically metabolites, in body fluidssuch as blood, typically whole blood, plasma, serum, urine, saliva,interstitial fluid or other body fluids. Further devices are known formeasuring activating times, e.g., a thrombin activation time measurementfor coagulation monitoring. Without restricting the scope of the presentdisclosure, in the following, mainly reference is made to thedetermination of glucose as an exemplary and typical analyte.

The determination of an analyte concentration, e.g., of blood glucose,as well as a corresponding medication is an essential part of the dailyroutine for many diabetics. In order to increase convenience and inorder to avoid restricting the daily routine by more than a tolerabledegree, portable devices and test elements are known in the art, such asfor measuring blood glucose concentration during work, leisure or otheractivities away from home. In the meantime, many test devices arecommercially available. A large number of test devices and test systemsare known which are based on the use of test elements in the form oftest strips. Applications are known, in which a multiplicity of teststrips is provided by a magazine, wherein a test strip from the magazineautomatically may be provided with the testing device. Otherapplications, however, are known in which single test strips are used,which are inserted into the testing device manually by a user. Therein,typically, the end of the test strip is adapted to be inserted into thetesting device and for detecting the analyte, wherein the opposing endof the test strip serves as a handle enabling the user to push the teststrip into the testing device or to remove the test strip from thetesting device. For applying the sample to the test element, typicaltest elements provide at least one sample application site, such as acapillary opening in capillary test elements or a sprite net in opticaltest strips having a top dosing system. Test strips of this type arecommercially available, e.g., under the trade name Accu-Chek Active®.Alternatively to home care applications, such test elements may be usedin professional diagnostics, such as in hospital applications.

In many cases, for detecting the analyte, test elements are used, suchas test strips, which comprise one or more test fields having one ormore test chemistries. The test chemistries are adapted to change one ormore detectable properties in the presence of the analyte to bedetected. Thus, electrochemically detectable properties of the testchemistry and/or optically detectable properties of the test chemistrymay be changed due to the influence of the presence of the analyte. Forpotential test chemistries which may be used within the presentdisclosure, reference may be made to J. Hones et al.: DiabetesTechnology and Therapeutics, Vol. 10, Supplement 1, 2008, S-10 to S-26.However, other types of test chemistries may be used within the presentdisclosure.

In general, the detection of the at least one analyte can be performedby using an electrochemical biosensor. Electrochemical biosensors, e.g.,an electrochemical biosensor for determining the concentration ofglucose in a blood sample, use enzymes to provide a specific reactionwith the analyte. Glucose gets specifically oxidized by an enzymeco-factor, which is permanently or temporally bound to an enzyme. With apermanently bound co-factor a second redox active substance is required,which, as an electron acceptor, gets reduced by a reaction with theenzyme co-factor. By a diffusion process, the reduced substance is movedto an electrode, where, by applying a suitable redox potential, it getsre-oxidized. The transferred electrons can be measured by the resultingcurrent as a measure for the glucose concentration. Further examples areelectrochemical biosensors for measuring activation times, wherein acertain status of a stimulated biological process in the test sample isreached. An example is a coagulation time biosensor test strip, whereinthe activation of the protease thrombin is detected when the activatedthrombin cuts off a redox tag from an artificial peptide substrate. Thereduced redox tag can be detected by applying a suitable voltage betweenat least two electrodes and monitoring an amperometric response.

In electrochemical biosensors amperometric or voltammetric measurementmethods are used. However, multiple side effects, e.g., ambientconditions like the ambient temperature and humidity, can causesignificantly wrong concentration results, especially in case the testedsample is whole blood. The temperature, and indirectly the humidity, maychange a diffusion velocity in a test zone, resulting in varying overallreaction velocities, diffusion and electrode processes. Furthermore, themeasurement result may be influenced by properties of the blood sample,like sample temperature, hematocrit level or, in case of an additionalimpedance measurement, also from ionic strength of the sample. Inaddition, blood samples can contain substances which cause complexinterferences with the analytical detection reaction, especially whenblood samples from critically ill patients in hospitals are used, whereconcentrations of interfering substances, like intravenouslyadministered drugs, can reach high concentrations. The ionic strength,hematocrit and protein levels of these blood samples can frequently beat extreme levels. Accuracy of the measurement results may also belimited by the manufacturing process tolerances within a production lotof the produced test strips. For example, electrode surface variationsand electrode distance variations may occur, caused by varying reagentcoating thicknesses. Further, a behavior of the test strips can bechanged by aging under storage conditions or the time of exposure beforestarting the actual measurement. Furthermore, changes of an overall testarrangement and conditions during the detection process such as reagentdissolving, sample evaporation, changes of the active electrode surfaceand ambient temperature changes may influence the measurement result. Inaddition, several kinds of gradient effects have to be considered. Forexample, the sample temperature may change during the detection phase;concentrations of reactive components may change due to slowinterference reactions; diffusion layers may be disturbed by movementsof the sample due to sample dosing effects; reagent layer homogeneitymay change during test time due to dissolving, swelling or dismixingeffects; the sample can partially dry off due to evaporation effects orintermediate reaction products may be instable or volatile. Furthermore,in test strip based systems a steady state situation may never bereached.

Commercially available test strip based blood glucose systems use atemperature sensor in the connected meter to correct the effect ofvarying ambient temperatures. However, the test strips may havedifferent temperatures than the temperature sensor in the meter. Inaddition, further effects like sample temperature and changing sampletemperatures during test time are not considered. Other systems analyzea progression of the amperometric measurement curves during test time orimplement a series of direct current (DC) pulses with same or reversedpolarity to correct certain interference effects. However, by using DCmethods only, not all relevant interference effects can bedistinguished, such that sufficient error compensation may not bepossible, in particular, because signal level and slopes differdepending on the analyte concentration and other varying properties ofthe test sample. Other systems use additional electrodes sensitive tocertain interference effects and sample properties to compensateinterference effects. However, a measurement result has to be calculatedfrom responses of different electrodes, such that accuracy may belimited by a geometrical error summation of individual signal noise. Inaddition, implementation of multiple electrodes may increase complexityof the test strips and, therefore, production cost and manufacturingrobustness.

Interference effects can be estimated independently from the analyteconcentration by using a combination of an impedance measurement and anamperometric measurement.

Despite the advantages and progress achieved by the above-mentioneddevelopments, some significant technical challenges remain. Theimpedance measurement may introduce additional interference effectswhich may have a significant impact on the impedance measurement but noton the amperometric measurement. For example, the varying ionic strengthof a blood sample may cause additional imprecision to the measurementresult. Furthermore, in such methods different frequency steps may beapplied in a sequential manner and the amperometric measurement isperformed afterwards or before the impedance measurement. As aconsequence, if the overall test conditions during the stepwise executedtest sequence change with time, the amperometric measurement can beover- or undercompensated. For example, if the sample temperaturechanges during test time, the temperature at the time of the impedancemeasurement could be different compared to the time when theamperometric measurement is executed. As a result, an additional biasmay be caused by temperature gradient effect. Further, for example, ifan impedance response is determined only during a short time interval ofa total test time, the relevant information at any time during the testtime may not be observed. Furthermore, if several interference effectsand gradients have to be compensated for, compensation may beinsufficient. Not all interfering effects can be compensated by using asequential impedance measurement and amperometric measurement. Forexample, if redox active interference substances from parenteraladministered drugs reacts with the used redox mediator in the detectionreagents, high direct current response biases may occur which may not beobserved in the alternating current impedance response.

BRIEF SUMMARY

It is against the above background that the embodiments of the presentdisclosure provide certain unobvious advantages and advancements overthe prior art. In particular, the inventors have recognized a need forimprovements in a method and a device for determining at least oneanalyte in a bodily fluid.

Although the embodiments of the present disclosure are not limited tospecific advantages or functionality, it is noted that the presentdisclosure at least partially avoid the shortcomings of known devicesand methods of this kind and which at least partially address theabove-mentioned challenges. Specifically, reliability of measurementresults of a concentration of at least one analyte in bodily fluid areimproved.

In accordance with one embodiment of the present disclosure, a methodfor determining a concentration of at least one analyte in bodily fluidis provided, the method comprising the following steps: at least onesignal generation step, wherein at least one excitation voltage signalis generated by at least one signal generator device, wherein theexcitation voltage signal comprises at least one poly frequentalternating current (AC) voltage and at least one direct current (DC)voltage profile, wherein the poly frequent AC voltage comprises at leasttwo frequencies; at least one signal application step, wherein theexcitation voltage signal is applied to at least two measurementelectrodes, which are in contact with the bodily fluid and which areadapted to determine the analyte electrically or electrochemically; atleast one measurement step, wherein a response is measured by using themeasurement electrodes; at least one evaluation step, wherein an ACcurrent response for each frequency and a DC current response areevaluated from the response by at least one evaluation device, andwherein for each frequency at least one phase information and at leastone impedance information is evaluated from the AC current response bythe evaluation device; at least one determination step, wherein theconcentration of the analyte is determined from the DC current responseand from one or both of the phase information and impedance informationby using at least one predetermined relationship, wherein the AC voltageand DC profile are superimposed to form the excitation voltage signal.

In accordance with another embodiment of the present disclosure, ananalytical device for determining a concentration of at least oneanalyte in bodily fluid is provided, the analytical device comprising:at least one signal generator device adapted to generate at least oneexcitation voltage signal, wherein the excitation voltage signalcomprises at least one poly frequent alternating current (AC) voltageand at least one direct current (DC) voltage profile, wherein the polyfrequent AC voltage comprises at least two frequencies; at least onemeasurement unit, wherein the measurement unit is adapted to receive aresponse, at least one evaluation device adapted to evaluate an ACcurrent response for each frequency and a DC current response from theresponse, wherein the evaluation device is adapted to evaluate for eachfrequency at least one phase information and at least one impedanceinformation is evaluated from the AC current response, wherein theevaluation device is adapted to determine a concentration of the analytefrom the DC current response and from one or both of the phaseinformation and impedance information by using at least onepredetermined relationship, wherein the AC voltage and DC profile aresuperimposed to form the excitation voltage signal.

Embodiments of the disclosed method and device for determining aconcentration of at least one analyte in bodily fluid have the featuresof the independent claims. Typical embodiments, which might be realizedin an isolated fashion or in any arbitrary combination, are listed inthe dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of the embodiments of the presentdisclosure can be best understood when read in conjunction with thefollowing drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 shows an embodiment of a method according to the presentdisclosure;

FIG. 2 shows an embodiment of test element analysis system;

FIG. 3 shows an exemplary embodiment of an analytical device;

FIG. 4 shows an embodiment of a composition of a poly frequent ACvoltage;

FIG. 5 shows development over time of an excitation voltage signal usingan amperometric voltage profile as DC profile and DC response;

FIG. 6 shows development over time of a slope of the DC response;

FIG. 7 shows an example of a selection of DC time points;

FIG. 8 shows experimental results for a face to face electrode testelement;

FIGS. 9 and 10 show an example of an excitation voltage signal using acombination of a cyclic voltammetry superimposed with DC pulses andadditionally superimposed with a poly frequent AC voltage; and

FIGS. 11 to 13 show experimental results for a glucose test strip forthe excitation signal of FIGS. 9 and 10.

Skilled artisans appreciate that elements in the figures are illustratedfor simplicity and clarity and have not necessarily been drawn to scale.For example, the dimensions of some of the elements in the figures maybe exaggerated relative to other elements to help improve understandingof the embodiments of the present disclosure.

DETAILED DESCRIPTION

As used in the following, the terms “have”, “comprise” or “include”, orany arbitrary grammatical variations thereof, are used in anon-exclusive way. Thus, these terms may both refer to a situation inwhich, besides the feature introduced by these terms, no furtherfeatures are present in the entity described in this context and to asituation in which one or more further features are present. As anexample, the expressions “A has B”, “A comprises B” and “A includes B”may refer both to a situation in which, besides B, no other element ispresent in A (i.e., a situation in which A solely and exclusivelyconsists of B) and to a situation in which, besides B, one or morefurther elements are present in entity A, such as element C, elements Cand D or even further elements.

Further, it shall be noted that the terms “at least one”, “one or more”or similar expressions indicating that a feature or element may bepresent once or more than once, typically will be used only once, whenintroducing the respective feature or element. In the following, in mostcases, when referring to the respective feature or element, theexpressions “at least one” or “one or more” will not be repeated,non-withstanding the fact that the respective feature or element may bepresent once or more than once.

Further, as used in the following, the terms “preferably”, “morepreferably”, “particularly”, “more particularly”, “specifically”, “morespecifically”, “typically”, “more typically”, or similar terms are usedin conjunction with optional features, without restricting alternativepossibilities. Thus, features introduced by these terms are optionalfeatures and are not intended to restrict the scope of the claims in anyway. The disclosure may, as the skilled person will recognize, beperformed by using alternative features. Similarly, features introducedby “in an embodiment of the disclosure” or similar expressions areintended to be optional features without any restriction regardingalternative embodiments of the disclosure, without any restrictionsregarding the scope of the disclosure and without any restrictionregarding the possibility of combining the features introduced in such away with other optional or non-optional features of the disclosure.

In a first aspect of the present disclosure, a method for determining aconcentration of at least one analyte in bodily fluid is provided. Themethod comprises the method steps as given in the independent claims andas listed as follows. The method steps may be performed in the givenorder. However, other orders of the method steps are feasible. Further,one or more of the method steps may be performed in parallel and/or in atime overlapping fashion. Further, one or more of the method steps maybe performed repeatedly. Further, additional method steps may be presentwhich are not listed.

The method comprising the following steps:

-   -   at least one signal generation step, wherein at least one        excitation voltage signal is generated by at least one signal        generator device, wherein the excitation voltage signal        comprises at least one poly frequent alternating current (AC)        voltage and at least one direct current (DC) voltage profile,        wherein the poly frequent AC voltage comprises at least two        frequencies;    -   at least one signal application step, wherein the excitation        voltage signal is applied to at least two measurement        electrodes;    -   at least one measurement step, wherein a response is measured by        using the measurement electrodes;    -   at least one evaluation step, wherein an AC current response for        each frequency and a DC current response are evaluated from the        response by at least one evaluation device, and wherein for each        frequency at least one phase information and at least one        impedance information is evaluated from the AC current response        by the evaluation device;    -   at least one determination step, wherein the concentration of        the analyte is determined from the DC current response and from        one or both of the phase information and impedance information        by using at least one predetermined relationship.

As used herein, the term “bodily fluid” generally refers to a fluidwhich typically is present in a body or body tissue of a user or thepatient and/or which may be produced by the body of the user or thepatient. In particular, the bodily fluid may be a sample of bodilyfluid. As an example for body tissue, interstitial tissue may be named.Thus, as an example, the body fluid may be selected from the groupconsisting of blood and interstitial fluid. For example, the bodilyfluid may be whole blood. However, additionally or alternatively, one ormore other types of body fluids may be used, such as saliva, tear fluid,urine or other body fluids. Generally, an arbitrary type of body fluidmay be used.

In particular, the concentration of at least one analyte may bedetermined in a sample of bodily fluid. As used herein, the term“sample” may refer to an arbitrary material or combination of materialstaken for an analysis, testing or investigation. The sample may be alimited quantity of something which is intended to be similar to andrepresent a larger amount. However, the sample may also comprise a fullspecimen. The sample may be a solid sample, a liquid sample or a gaseoussample or a combination of these. Specifically, the sample may be afluid sample, i.e., a sample which fully or partially is in a liquidstate and/or in a gaseous state. A quantity of the sample may bedescribable in terms of its volume, mass or size. However, otherdimensions are feasible. The sample may comprise only one material oronly one compound. Alternatively, the sample may comprise severalmaterials or compounds.

As further used herein, the term “analyte” may refer to an arbitraryelement, component or compound which may be present in a body fluid andthe concentration of which may be of interest for a user or a patient.Typically, the analyte may be or may comprise an arbitrary chemicalsubstance or chemical compound which may be part of the metabolism ofthe patient, such as at least one metabolite. As an example, the atleast one analyte may be selected from the group consisting of glucose,cholesterol, triglycerides and lactate. Additionally or alternatively,however, other types of analytes may be used and/or any combination ofanalytes may be determined.

As generally used within the present disclosure, the terms “user” and“patient” may refer to a human being or an animal, independent of thefact that the human being or animal, respectively, may be in a healthycondition or may suffer from one or more diseases. As an example, thepatient may be a human being or an animal suffering from diabetes.However, additionally or alternatively, the disclosure may be applied toother types of users or patients.

The term “determining a concentration of at least one analyte in bodilyfluid” generally refers to a quantitative detection of the at least oneanalyte. As a result of the determination, at least one signal, such asat least one measurement signal, and/or at least one measurement valuemay be produced and/or provided which characterizes an outcome of thedetermination. The signal specifically may be or may comprise at leastone electronic signal such as at least one voltage and/or at least onecurrent. The at least one signal may be or may comprise at least oneanalogue signal and/or may be or may comprise at least one digitalsignal.

As used herein, the term “at least one excitation voltage signal”generally refers to at least one arbitrary voltage signal applicable tothe bodily fluid, e.g., by using at least two electrodes. The excitationvoltage signal may be applied during at least one test sequence, forexample a time sequence. The excitation voltage signal comprises atleast one poly frequent AC voltage and at least one DC voltage profile.

As used herein, the term “AC voltage”, also denoted as AC excitation,refers to an alternating voltage having a periodic signal waveform, forexample a sine or triangle waveform. As used herein, the term “polyfrequent”, generally refers to at least one AC voltage comprising atleast a first frequency and at least one second frequency, wherein thefirst and second frequencies differ. The poly frequent AC voltagecomprises at least two frequencies. The AC voltage may have a sine ortriangle waveform. Other wave forms are feasible. For example, the ACvoltage may comprise at least two AC sine waves having differentfrequencies. The AC voltage may comprise at least two AC sine waveshaving different frequencies, wherein the two AC signals aresuperimposed. The poly frequent AC voltage may comprise three, four ormore frequencies. The frequencies may be in the range of 500 Hz to 20kHz. The poly frequent AC voltage may comprise four superimposedfrequencies, for example, 1 kHz, 2 kHz, 10 kHz and 20 kHz.

The AC voltage may have a magnitude or amplitude such that no faradiccurrent response is generated. For example, the magnitude of the ACvoltage may be less than 30 mV rms (root mean square).

As used herein, the term “DC voltage profile” generally refers to anarbitrary DC voltage having a time profile. As used herein, the term “DCvoltage” refers to a direct voltage having successive phases and/or rampsections of essential constant voltage. Time span of such phases or rampsections may be more than 1/10 seconds. As used herein, “essentialconstant” generally refers to DC voltage profile having ramps with arate of increase up to 1 V/s. The DC voltage profile may comprise a timeprofile. As used herein, the term “time profile” refers to change of DCvoltage during one or more of a measurement cycle or test cycle, ameasurement interval or test interval, a measurement sequence or testsequence, a whole or total measurement or test time. The DC voltage maybe changed and/or may be varied continuously or stepwise. For example,the DC voltage may comprise at least one step sequence. For example, theDC voltage profile may comprise at least two voltage steps. For example,the DC voltage profile may comprise three, four or five voltage steps.Even more voltage steps are feasible. The steps of the DC voltageprofile may be selected to allow for a differentiation between ananalytical reaction and various interference reactions. The DC voltagemay have a rectangular waveform. Other waveforms are feasible.

The DC voltage profile may be selected from the group consisting of: avoltammetric voltage profile; an amperometric voltage profile.

As DC voltage profiles all kinds of voltammetric profiles ofvoltammetric methods, for example cyclic voltammetry or differentialpulse voltammetry, may be used. For example, in cyclic voltammetry theDC voltage, e.g., applied between a working electrode and a counter orreference electrode, may be ramped linearly versus time. In oneembodiment of cyclic voltammetry, the DC voltage profile may compriseincreasing, e.g., in steps, the DC voltage from a start value to a firstturning point, subsequent decreasing from the first turning point to asecond turning point and subsequent increasing from the second turningpoint to the start value. Using voltammetric methods like cyclicvoltammetry or differential pulse voltammetry allows obtaininginformation that can be used to at least partially compensateinterference effects of redox active substances, which reacts with anelectro mediator or measuring electrodes. By using voltammetry,interference substances will get reduced or oxidized at differentpotentials compared to the redox mediator used to indicate theanalytical detection. Voltammetric methods may allow obtaininginformation that can be used to identify and compensate for interferingeffect. Specifically, voltammetric methods like cyclic voltammetry anddifferential pulse voltammetry may allow compensating for an influenceof substances in blood, which reduce in competition to a substrate- orenzyme-system the redox mediator and may cause a positive biased testresult. For example, the voltage profile may comprise at least onesequence configured to differentiate such interferences, for example aDC-measurement having a different polarity. The simultaneous impedancemeasurement during this sequence can be used to compensate forinfluences due to temperature of the sample and/or viscosity of a wettedreagent layer.

The DC voltage profile may be or may comprise an amperometric voltageprofile. The amperometric voltage profile may comprise different voltagesteps, for example a series of amperometric steps at different voltages.The DC voltage profile may be or may comprise at least one amperometricDC voltage step sequence comprising at least two different voltagesteps. For example, the DC voltage profile may comprise three voltagesteps, wherein in a first voltage step the DC voltage amounts to 500 mV,in a second voltage step the DC voltage amounts to 200 mV and in a thirdvoltage step the DC voltage amounts to −400 mV. However, other voltagesteps are feasible. Using information from a time profile of anamperometric response allows for compensation of one or more of unwantedside reaction of the redox mediator with an interfering substance and/orof different reaction velocity compared to an actual detection reactionand/or of substances in a sample directly interfering with electrodes.Furthermore, using a time profile of an amperometric response allowscompensating aging effects from storage times or exposure times betweenopening a primary test element packaging and an actual measurement.Aging effects may occur due to losses of activity of enzymes as specificagent in the detection reagent. Another aging or exposure time effectmay be a mediator degradation, which can cause increasing blank currentsor signal loss. By using amperometric response time profiles, agingeffects and/or influences of aging effects can be determined. By usingamperometric response time profiles most of biases caused by redoxactive interfering substances, enzyme activity loss or redox mediatordegradation and ambient temperature effects may be compensated. Inparticular, compensation of effects of interfering substances and/ortemperature effects using amperometric response time progression may bepossible in case reaction velocities of competing reaction differsignificantly and if the impedance measurement is performedsimultaneously, i.e., not only after completion of the reaction butduring development of reaction, in particular during preceding chemicalreactions.

As further used herein, the term “signal generator device” generallyrefers to a device, for example a voltage source, being configured togenerate a voltage signal. The signal generator device may comprise atleast one AC-voltage source and at least one DC-voltage source. Thesignal generator device may be adapted to generate at least one polyfrequent AC voltage. For example, the signal generator may be adapted togenerate multiple AC voltage signals each having different frequenciesand to sum up the multiple AC signals. The signal generator device maybe adapted to generate at least one DC profile.

The AC voltage and DC profile may be superimposed to form the excitationvoltage signal. The signal generator device may be adapted to apply theAC voltage and DC profile simultaneously to the bodily fluid. The signalgenerator device may be adapted to apply the excitation voltage signalcomprising superimposed poly frequent AC voltage and DC profile to thebodily fluid. The poly frequent AC voltage and DC profile may be appliedto the measurement electrodes without offset time and/or time delay.

The signal generator device may be part of measurement electronicsand/or may be connected to the measurement electronics. The signalgenerator may be part of a measurement electronics, such as of anevaluation device, or may be designed as a separate device.

The excitation voltage signal is applied to at least two measurementelectrodes in at least one signal application step. As used herein, theterm “measurement electrodes” generally refers to electrodes, e.g., ofat least one test element, which are in contact with the bodily fluidand which are adapted to determine the analyte electrically orelectrochemically. The method may comprise a sample application step,wherein the sample of a bodily fluid is brought in contact with themeasurement electrodes. For example, in the sample application step atest element having a sample application opening and a capillary channelmay be used. Thus, the sample of bodily fluid may be applied to thesample application opening and may be transported by the capillarychannel to the measurement electrodes. Alternatively, in the sampleapplication step the sample may be brought directly in contact with theelectrodes, for example using a test element havingface-to-face-electrodes.

As used herein, the term “electrode” may generally refer to an arbitraryelement which is configured to or which is usable to electrically orelectrochemically detect the analyte. The at least two measurementelectrodes may be embodied such that an electrochemical reaction maytake place at one or more of the electrodes, such as one or more workingelectrodes. Thus, the electrodes may be embodied such that an oxidationreaction and/or reduction reaction may take place at one or more of theelectrodes. The electrochemical detection reaction may be detected bycomparing one or more electrode potentials, such as an electrostaticpotential of a working electrode with an electrostatic potential of oneor more further electrodes, such as a counter electrode or a referenceelectrode. Generally, the two or more measurement electrodes may be usedfor one or more of an amperometric measurement and/or a voltammetricmeasurement.

The at least two electrodes may comprise at least one working electrode.As used herein, the term “working electrode” refers to an electrodebeing adapted for or being usable for performing at least oneelectrochemical detection reaction for detecting the at least oneanalyte in the body fluid. The working electrode may have or may bebrought in contact with at least one test chemical being sensitive tothe analyte to be detected. The at least one test chemical may form atleast one test chemical surface which may be in contact with the atleast one body fluid. The at least two electrodes may further compriseat least one counter electrode. As used herein, the term “counterelectrode” refers to an electrode adapted for performing at least oneelectrochemical counter reaction and adapted for balancing a currentflow required by the detection reaction at the working electrode.Additionally or alternatively, the at least two electrodes may furthercomprise at least one reference electrode. The reference electrode mayhave a stable and well-known electrode potential. The electrodepotential of the reference electrode may typically be highly stable. Thecounter electrode and the reference electrode may be one of a commonelectrode or two separate electrodes.

In the at least one measurement step, a response is measured by usingthe measurement electrodes. The response may be measured at differentmeasurement time points. The response may be measured continuously or atselectable and/or adjustable measurement time points. The response overtime may be measured by using selectable and/or adjustable time units.For example, the response may be measured every tenth of a second oreven more often. As used herein, the term “response” generally refers toa response signal generated by the at least two measurement electrodesin response to the applied excitation voltage signal. The response maybe a current response. The response may comprise multiple signals. Theresponse may comprise an AC and DC response. As used herein, the term“measurement” generally refers to a quantitative and/or qualitativedetermination of the response, e.g., the current signal. As used herein,“measurement time point” generally refers to an arbitrary point in timeand/or arbitrary period of time, in particular a time interval, duringthe determination of the concentration of the analyte, i.e., during oneor more of a measurement cycle or test cycle, a measurement interval ortest interval, a measurement sequence or test sequence, a whole or totalmeasurement or test time, at which a response is determined. Themeasurement time points may be at different time points during testsequence, for example at different excitation voltages of the DCprofile.

The method comprises at least one evaluation step, wherein an AC currentresponse for each frequency and a DC current response are evaluated fromthe response by at least one evaluation device, and wherein for eachfrequency at least one phase information and at least one impedanceinformation is evaluated from the AC current response by the evaluationdevice.

As used herein, the term “evaluation device” generally refers to anarbitrary device being configured to derive at least one item ofinformation from data. The evaluation device may be configured to derivethe at least one item of information regarding the presence and/orconcentration of the analyte in the body fluid or a parameter of thebody fluid from at least one signal. The evaluation device may beconfigured to evaluate the response. As an example, the evaluationdevice may be or may comprise one or more integrated circuits, such asone or more application-specific integrated circuits (ASICs), and/or oneor more data processing devices, such as one or more computers,typically one or more microcomputers and/or microcontrollers. Additionalcomponents may be comprised, such as one or more preprocessing devicesand/or data acquisition devices, such as one or more devices forreceiving and/or preprocessing of the electrode signals, such as one ormore converters and/or one or more filters. Further, the evaluationdevice may comprise one or more data storage devices. Further, asoutlined above, the evaluation device may comprise one or moreinterfaces, such as one or more wireless interfaces and/or one or morewire-bound interfaces. The evaluation device may comprise a bloodglucose meter, for example a test strip based meter, an insulin pump, amicroprocessor, a cellular phone, a smart phone, a personal digitalassistant, a personal computer, or a computer server.

The evaluation device may be adapted to split up and/or to separate theresponse into the phase information and impedance, i.e., imaginary andreal components, information for each frequency of the AC currentresponse and the corresponding DC current response. The method maycomprise evaluating for each frequency at least one real and imaginarypart of admittance from the AC current response by the evaluationdevice. In particular, the evaluation device may be adapted to evaluatefor each frequency at least one real and imaginary part of admittancefrom the AC current response. The term “impedance” or “impedanceinformation” refers to complex impedance and/or admittance information.Generally, the complex impedance Z refers to opposition of a circuit toa current in case of applying an excitation voltage and can be describedas Z=R+iX, wherein real part R is the ohmic resistance and imaginarypart X is the reactance. In case of applying a DC excitation voltageonly, the impedance comprises only real parts, whereas in case ofapplying superimposed AC excitation voltage additionally comprisesimaginary parts. In polar form the complex impedance can be described byphase angle and magnitude. Thus, the term “phase information” generallyrefers to information on the phase angle. The admittance is the inverseof the impedance. The admittance Y and impedance Z can be converted intoeach other Y=Z⁻¹=1/R+iX=(1/R²+X²) (R−iX). Admittance is a complex numberand can be described in polar form by phase angle and magnitude. As usedherein, the terms “AC current response” and “DC current response”generally refer to AC and DC portions or parts of the response. The ACcurrent response and the DC current response may be separated withrespect to frequency range. The evaluation device may be adapted toclassify a portion of the current response as AC or as DC with respectto a predetermined frequency range. The evaluation device may compriseat least one electronic filter, e.g., a two-way analog electronicfilter, adapted to separate the response into AC current response andthe corresponding DC current response between about 100 Hz and 500 Hz.The evaluation device may be adapted to separate the response into slowDC current response and the fast changing AC current response. Forexample, the evaluation device may comprise at least one transimpedanceamplifier adapted to amplify response signals dependent on frequency.Subsequently, response signals may be separated by a crossover. ACcurrent response over 500 Hz, in particular in a frequency range from500 to 20 kHz, may be evaluated periodically and DC current responsehaving a rate of increase below 1 V/s is evaluated as time progression.Below 100 Hz the response may be classified as DC current response andabove 500 Hz the response may be classified as AC current response. Inthe evaluation step the AC current response and the DC current responsemay be separated using at least one two-way analog electronic filter,which splits the signals between about 100 Hz and 500 Hz, wherein below100 Hz the response is analyzed as DC and above 500 Hz it is analyzed asAC. The evaluation device may comprise at least one frequency analyzer.Thus, the DC current response and the AC current response may bedetermined simultaneously, in particular as one response. Thus, the DCcurrent response and the AC current response may be determined and/ormeasured without offset time and/or time delay.

The method comprises at least one determination step, wherein theconcentration of the analyte is determined from the DC current responseand from one or both of the phase information and impedance informationby using at least one predetermined relationship. The concentration ofthe analyte may be determined by the evaluation device, e.g., by atleast one computing device of the evaluation device.

In the determination step the concentration of the analyte may bedetermined in consideration of interference effects and productiontolerances. The interference effects may be selected from the groupconsisting of ambient conditions, in particular temperature andhumidity; sample properties, in particular sample temperature,hematocrit level, protein level, ionic strength. By applying theexcitation voltage signal composed AC voltage having differentfrequencies and the DC voltage profile it may be possible to get thebest possible performance, e.g., from a test strip based analyteconcentration or sample property measurement in a whole blood sample, byconsidering all relevant interference effects and strip productiontolerances. The phase information and/or at least one impedanceinformation of each frequency of the AC current response in combinationwith the DC current response may allow obtaining differentiableinformation of all those effects. For example, information from morethan one frequency may allow differentiating between differentinterference effects like temperature and hematocrit. Limitations fromall kind of gradient effects due to changes of the test conditionsduring the ongoing test time, especially when information from appliedDC voltage profiles or amperometric time progression information areincluded, may be avoided by obtaining information from the impedancemeasurement simultaneously with each DC time point of the voltageprofile or time trace, which later is included in the concentrationcalculation.

Known methods comprising usage of DC profiles like voltammetric methodsand/or profiles of an amperometric response do not consider anddetermine information from impedance measurements. However, thelimitation of these known methods may be that during requiredmeasurement time properties of a test element electrochemical cells arenot constant, because all kinds of gradient effects, such as sampletemperature, sample-reagent viscosity and/or ongoing capillary filling,may occur. Furthermore, the measured time profiles or voltage profilesmay depend on certain properties of the tested sample, especially if itis a blood sample. These properties may be, for example, the hematocritcontent, which has a significant impact on the diffusion of the activeingredients in detection reagent mixed with the sample. Other propertiesmay have an impact on the electro conductivity of a blood sample, whichdepends on the protein content, the lipids content or the ionicstrength, e.g., blood sample from critically ill patients. Furthermore,such methods cannot estimate effects of varying ambient and sampletemperatures, process tolerances with impact on the electrochemical cellgeometry, reagent layer thickness and sample dosing effects. Theseeffects can be estimated by performing an AC impedance measurementbetween the measuring electrodes, when multiple frequencies are appliedand the response per frequency is analyzed. Applying a poly frequent ACvoltage and DC profile and determining impedance information from eachfrequency of the AC current response simultaneously with the DC currentresponse may allow obtaining all required information to correct the DCmeasurement at the same time point and, thus, take regard of thegradient effects during the overall test time. The method may allowobtaining measurement signals, which comprise differentiable informationof the relevant effects. The method according to the present disclosuremay allow the achievement of the best possible performance, for exampleaccuracy of a test element, e.g., a test strip, based analyteconcentration or sample property measurement in whole blood, by allowingconsideration of all relevant interference effects and strip productiontolerances.

As used herein, the term “determination of the concentration of theanalyte” generally refers to quantitative and/or qualitativedetermination of the concentration of the analyte. As used herein, theterm “predetermined relationship” refers to a known or determinablerelationship between the concentration of the analyte and the DC currentresponse, the phase information and impedance information. Therelationship can be determined or determinable empirically, analyticallyor else semi-empirically. The relationship may comprise at least onecalibration curve, at least one set of calibration curves, at least onefunction or a combination of the possibilities mentioned. One or aplurality of calibration curves can be stored, for example in the formof a set of values and the associated function values thereof, forexample in a data storage device and/or a table. Alternatively oradditionally, however, the at least one calibration curve can also bestored, for example in parameterized form and/or as a functionalequation. Various possibilities are conceivable and can also becombined. The predetermined relationship may be provided in the form ofat least one look-up table and/or in the form of at least onemathematical formula. The predetermined relationship may be depositedand/or stored, for example in a storage of the evaluation device. Themethod may comprise determining a predetermined relationship of theconcentration of the analyte and the DC current response, the phaseinformation and impedance information.

The evaluation device may be adapted to determine the predeterminedrelationship. The evaluation device may be adapted to providemathematical functions and weighting coefficients which, for example,may be stored in a data storage and/or look-up table of the evaluationdevice. The method may comprise at least one training step, wherein thepredetermined relationship is determined. The predeterminedrelationship, in particular weighting coefficients of the predeterminedrelationship, may be one or more of selected, determined and verified bymathematical methods selected from the group consisting of multivariateanalysis, multilinear principal component analysis, neuronal nets,moving mesh, lasso method, boosted random forest and bootstrapping, onat least one training data set. The training data set may be collectedby performing co-variance studies. The training data set may comprise asuitable number of repeated measurements, for example with homogenousproduced test elements and/or by applying a selected test sequence withconnected electronic circuitry of a measurement device, for example ameter. To obtain the training data set the analyte concentration of eachtest sample may be determined with a reference method, for examplehexokinase method in case of a glucose concentration. To obtain thetraining data set each combination of relevant combined interferenceeffects may be tested across a relevant concentration range of theanalyte with a sufficient amount of repetition for each test combinationand test sample. For example, in the case of determining a glucoseconcentration in a blood sample the major interference effects may beambient temperatures, hematocrit level, ionic strength, plasmaconcentrations, lipid concentration or administered interferingsubstances, especially antioxidants. In case of test elements withunstructured face to face electrodes, which may not comprise separatefill sufficient detection electrodes, a fill level of a capillary may betested for the training data set generation. Another interference effectmight be the storage time in a primary test element package or an impactof environmental condition and exposer time of a test element, e.g., atest strip, when the test element is taken out of the package beforeexecuting the measurement. If the test element is not sufficientlyrobust versus these impacts, also these factors may be considered whenobtaining the training data set.

In one embodiment, the predetermined relationship may bebG=Σ _(i=1) ^(n) a _(i)DC_(i) e ^(Σ) ^(m=1) ^(f) ^(bm) ^(i) ^(Ym) ^(i)^(+cm) ^(i) ^(Pm) ^(i) ,wherein bG is the determined concentration of the analyte, i denotes thenumber of time points, wherein i, n, f and m are natural integernumbers, m denotes the number of frequencies, a_(i), b_(i), c_(i) areweighting coefficients, Y_(mi) are admittance values from AC response atdifferent frequencies at time points, P_(mi) are phase angle values fromAC response at different frequencies at time points and DC_(i) are DCresponse values at selected DC response time points. This predeterminedrelationship may be used for test elements having coplanar electrodes,wherein the electrodes are arranged next to each other in themeasurement cell. The weighting coefficients a_(i), b_(i), c_(i) may bedeposited and/or stored, for example in a storage of the evaluationdevice. The weighting coefficients a_(i), b_(i), c_(i) may be one ormore of selected, determined and verified by mathematical methodsselected from the group consisting of multivariate analysis, multilinearprincipal component analysis, neuronal nets, moving mesh, lasso method,boosted random forest and bootstrapping, on at least one training dataset.

In one embodiment, the predetermined relationship may be

${{bG} = {\sum\limits_{i = 1}^{n}{\sum\limits_{m = 1}^{f}\left( {\frac{a_{m\; i}D\; C_{i}}{Y_{{({imag})}m\; i}} + \frac{b_{m\; i}D\; C_{i}}{Y_{{({real})}m\; i}}} \right)}}},$

wherein bG is the determined concentration of the analyte, i denotes thenumber of measurement time points, wherein i, n, f and m are naturalinteger numbers, m denotes the number of frequencies, a_(i) and b_(i)are weighting coefficients, Y_((imag)mi) and Y_((real)mi) are real andimaginary parts of admittance values from AC response at differentfrequencies at time points and DC_(i) are DC response values at selectedDC response time points. This predetermined relationship may be used fortest elements having face to face electrodes. This predeterminedrelationship may be in particular advantageous for test elements havingface to face electrodes, wherein electrodes are arranged at opposingfaces of the measurement cell, because it allows good correlation of allrelevant effects between DC and AC signals. In particular, thepredetermined relationship may be,

${{bG} = {\sum\limits_{\underset{i \neq j}{i,{j = 1}}}^{n}\left( {\frac{a_{i}D\; C_{i}}{Y_{i}} + {b_{i}\left( {\frac{D\; C_{i}}{Y_{i}} \cdot \frac{D\; C_{j}}{Y_{j}}} \right)}} \right)}},$

wherein bG is the determined concentration of the analyte, i and jdenote the number of measurement time points, wherein i, j and n arenatural integer numbers, a_(i), b_(i) and c_(i) are weightingcoefficients, Y_(i), and Y_(j) are either real or imaginary parts ofadmittance values from AC response at different frequencies at timepoints i and j. DC_(i), DC_(j) are DC response values at selected DCresponse time points.

In one embodiment, the predetermined relationship may be

${{bG} = {\sum\limits_{\underset{i \neq j}{i,{j = 1}}}^{n}{\sum\limits_{\underset{m \neq l}{m,{l = 1}}}^{f}\left( {\frac{a_{m\; i}D\; C_{i}}{Y_{{({imag})}m\; i}} + \frac{b_{m\; i}D\; C_{i}}{Y_{{({real})}m\; i}} + {c_{i}\left( {\frac{D\; C_{i}}{Y_{{({imag})}m\; j}} \cdot \frac{D\; C_{j}}{Y_{{({real})}{li}}}} \right)} + {d_{i}\left( {\frac{D\; C_{i}}{Y_{{({imag})}{lj}}} \cdot \frac{D\; C_{j}}{Y_{{({real})}m\; i}}} \right)}} \right)}}},$

wherein bG is the determined concentration of the analyte, i and jdenote the number of measurement time points, wherein i, j, n, f, m andl are natural integer numbers, m and l denote the number of frequencies,a_(i), b_(i) and c_(i), d_(i) are weighting coefficients, Y_((imag)mi),Y_((real)mi) Y_((imag)mj) and Y_((real)mj) are real and imaginary partsof admittance values from AC response at different frequencies at timepoints i and j and DC_(i), DCj are DC response values at selected DCresponse time points. This predetermined relationship may be used fortest elements having face to face electrodes.

The weighting coefficients may be determined by a moving mesh method.Alternatively neuronal net or multivariate regression methods orcombinations of these methods may be used. Other mathematical methods,e.g., the lasso method, may be used, to identify and select relevantobservables to reduce a total number in order to reduce complexity andimprove portability of the found model from the used training data onindependent collected verification data sets.

As outlined above, the excitation voltage signal may be applied duringat least one test sequence. As used herein, the term “test sequence”generally refers to an arbitrary period of time during which theexcitation voltage signal is applied. The AC and DC current response maybe determined at measurement time points continuously and/ornon-continuously during the at least one test sequence.

The method further may comprise at least one selection step, wherein inthe selection step from the measurement time points at least one DC timepoint is selected. From the measurement time points DC time points maybe selected which are used for determination of the analytical result.In the selection step from the measurement time points a number of DCtime point may be selected. For example, three, four, five, six, ten oreven twelve DC time points may be selected during at least one testsequence and/or during at least one voltage step of the excitationvoltage signal during the test sequence. Even a higher number of DC timepoints may be feasible. Additionally or alternatively, a replacement ofindividual DC time points by coefficients derived from a time-regressionmay be feasible. The DC time point may be a time point at which the DCresponse current is used in the determination step.

The measurement of AC response may be performed at different measurementtime points. In particular admittance values and phase angle values maybe determined for different measurement time points. The AC response maybe measured during at least one measurement time interval of the wholetest sequence. In the measurement time interval the AC response may beintegrated for calculation of the analytical result. For example, in themeasurement time interval at least one measurement vector may beintegrated for calculation of the analytical result. The measurementtime interval and/or measurement vector may be selected with respect totime development of the current response. Additionally or alternatively,at least two different measurement time points or at least onemeasurement time interval may be selected for calculation of theanalytical result.

The DC_(i) response value at the DC time point may fulfill certainquality conditions, such as time points which allow differentiation ofvarious interference effects.

The excitation voltage signal may be applied to the measurementelectrodes and the response is measured and evaluated and split up intothe phase and the impedance information for each frequency of the ACcurrent response and the corresponding DC response at that time point.The simultaneously obtained DC_(i) response values for a number of DCtime points may be picked from the whole test sequence and may be storedand, after the measurement, used to calculate the concentration. Themethod may comprise at least one storage step, wherein in the storagestep the DC current response is stored for a suitable number of timepoints of the test sequence, for example in at least one look-up table.The DC current response may be stored by the evaluation device, forexample in at least one data storage device and/or data carrier of theevaluation device. The number of selected DC time points and/or aselection of DC time points may depend on one or more of a quality oftime points, the DC profile such as profile shape and/orcharacteristics, length or duration of test sequence, expectedinterferences, time development of analyte reaction, kinetics of analytereaction. For example, the DC time points may be evenly spaced over aspecific period, e.g., the test sequence, or may be spaced at varyingintervals from one another. The DC time points may be selected such thatat least at each DC voltage step one DC time point is selected. Forexample, in case of three DC voltage steps, for each voltage step atleast four DC time points may be selected.

The method may comprise at least one calibration step. For example, themethod may comprise a lot calibration step, wherein the measuredresponse may be re-scaled in order to reduce interference effectsgenerated by test element production tolerances with impact on a testelement cell constant. Interference effects generated by test elementproduction tolerances with impact on the test element cell constant,e.g., capillary height and width, reagent thickness, may be reduced byre-scaling the measurement response. Based on test measurements withadjusted blood samples the measurement response may be re-scaled versusequivalent data obtained with a specially selected master lot. There-scaling may be applied directly on the measured response, i.e., theobservable. Scaling factors may be or may be determined from a ratio ofthe analytical result determined with a test element to be calibratedand the analytical result determined with a known test element, i.e., atest element having known properties. Additionally or alternatively,each of the mathematical terms of the predetermined relationship may bere-scaled. For example, the scaling factors may be or may be determinedfrom ratios of the each of mathematical terms for the test element to becalibrated and of the corresponding mathematical term determined with aknown test element. The measurement may be capable of identifying astrip lot directly from each test element to avoid calibration datamismatch. In the determination step, the concentration of the analytemay be determined by using information from the calibration steps.

The method further may comprise determining activation times, like thethrombin activation as an indicator for a blood coagulation time. Thetest element may comprise a reagent, which covers a working electrodeand at least one counter-reference electrode to allow an amperometriccurrent response, when a suitable DC voltage is applied. The reagent maycomprise a coagulation start reagent and a peptide substrate with alinked redox tag. At an end of a coagulation reaction in the bloodsample dosed to the test element, the protease thrombin may be activatedand cleavages the redox tag from the peptide substrate. When a suitableDC voltage is applied between the measurement electrodes, the start ofthe redox tag cut-off can be detected. The time from dissolving thereagent by the blood sample until the redox tag cleavage may be theactivation time. The activation time may be detected, if a predeterminedthreshold is exceeded, which may be stored, for example in theevaluation device. The current response may depend on the bloodhematocrit level and on the temperature. The test elements may bethermostatically controlled, e.g., to 37° C., in or to compensatetemperature sensitivity. The AC impedance may be used to correct theeffect of varying hematocrit levels, which influences the time when thethreshold is crossed and residual temperature variation. In knownmethods, e.g., sequential measurement with measuring the impedance atone time and the DC threshold exceeding at another time in dependency onthe coagulation properties of the sample, the correction performance maybe limited due to all kinds of gradient effects. These effects may be,for example ambient temperature variations, sample evaporation anddrying or reagent fluctuation. Instead, in the method according to thepresent disclosure simultaneous poly frequent AC and DC profile areapplied, such that the complex impedance measurement can be used, tocorrect the DC response always at the right time point, when thethreshold is crossed and also at time points, where other useful DCresponse information is collected, e.g., background current correctionor fail safe measurements.

The method may comprise a temperature calibration. The temperaturecalibration may comprise determining if a temperature, in particular ina dissolved reagent, is, during the measuring time, within allowedand/or predetermined limit. The temperature calibration may comprisecalibrating poly frequent impedance AC responses from the measured testelement with all relevant sample types versus a reference temperature.This method step may be performed in a climate chamber. By thetemperature calibration it is possible to determine during the totalmeasuring time, if the temperature is continuously in the allowed rangeand to compensate effects due to temperature and/or to issue an errormessage or warning. As used herein, the term “allowed range” refers toan allowed measurement deviation from a desired and/or selectedmeasurement value. For example, the allowed range may be an allowedmeasurement deviation from a desired and/or selected activation timedepending on the temperature. The allowed range may be determined and/orselected. Limits of the allowable range may be stored as fail-safelimits, e.g., within a memory of the analytical device, for example ofthe evaluation device.

The method, furthermore, may comprise at least one fail safe step. Theresponse from the simultaneous poly frequent AC and DC profileexcitations may be used to perform at least one fail safe step, whereinthe fail safe step may comprise determining if the analyteconcentration, i.e., a measured result, is valid within predeterminedlimits. For example, the predetermined limits may be between +/−7 mg/dl(for glucose concentrations below 100 mg/dl) and +/−10 percent (forglucose concentrations above 100 mg/dl) for 99% of all determinedanalytical results. The fails safe step may comprise issuing and/ordisplaying an error message in case the analyte concentration is notwithin the predetermined limits. In particular, the fails safe step maycomprise preventing issuing and/or displaying the analytical result andissuing and/or displaying an error message in case the analyteconcentration exceeds predetermined limits, for example +/−15 mg/dl/20%.The method may comprise determining failure modes, for example, if thetest element is out of specification, or sample and test conditions areoutside the claimed ranges or handling errors by the users. Thepredetermined relationship may be determined in consideration ofrelevant failure modes. For example, the respective mathematicalfunction and weighting coefficients and training data set may bedetermined and/or selected with respect to the relevant failure mode.The fail safe step may comprise storing, e.g., within a measurementengine electronic, for example, of the evaluation device, the determinedpredetermined relationship and determined analyte concentration. Thefail safe step may allow a measurement data consistency check. The failsafe step may comprise displaying a warning and/or error messages. Thefails safe step may comprise determining at least one identifier, forexample a formula, from a training data set which is suitable todifferentiate analytical results outside predetermined limits from“real” analytical results, i.e., analytical results within thepredetermined limits. The training data set may comprise incorrect orfaulty test elements. Furthermore, the fails safe step may comprisedetermining test values which are suitable to identify and/or to clearlydifferentiate specific fault cases. Test values corresponding to realanalytical results may lie within a predetermined test value rangeand/or may exhibit low scattering. Test values may be one or more of atleast one measurement value, a combination of a plurality of measurementvalues, e.g., products, ratios, differences. The fails safe step furthermay comprise using at least one decision tree matrix. For example, theanalytical result may be considered faulty in case a ratio of twomeasurement values, for example denoted as A and B, is above apredetermined first limit but smaller than a predetermined second limit,and if at the same time a third measurement value, denoted as C, minusthree times a fourth measurement value, denoted as D, is smaller than athird predetermined limit.

The disclosure further discloses and proposes a computer programincluding computer-executable instructions for performing the methodaccording to the present disclosure in one or more of the embodimentsenclosed herein, when the program is executed on a computer or computernetwork. Specifically, the computer program may be stored on acomputer-readable data carrier. Thus, specifically, one, more than oneor even all of method steps, as indicated above, may be performed byusing a computer or a computer network, typically by using a computerprogram.

The disclosure further provides and proposes a computer program producthaving program code means, in order to perform the method according tothe present disclosure in one or more of the embodiments enclosedherein, when the program is executed on a computer or computer network.Specifically, the program code means may be stored on acomputer-readable data carrier.

Further, the disclosure provides and proposes a data carrier having adata structure stored thereon, which, after loading into a computer orcomputer network, such as into a working memory or main memory of thecomputer or computer network, may execute the method according to one ormore of the embodiments disclosed herein.

The disclosure further proposes and provides a computer program productwith program code means stored on a machine-readable carrier, in orderto perform the method according to one or more of the embodimentsdisclosed herein, when the program is executed on a computer or computernetwork. As used herein, a computer program product refers to theprogram as a tradable product. The product may generally exist in anarbitrary format, such as in a paper format, or on a computer-readabledata carrier. Specifically, the computer program product may bedistributed over a data network.

Finally, the disclosure proposes and provides a modulated data signalwhich contains instructions readable by a computer system or computernetwork, for performing the method according to one or more of theembodiments disclosed herein.

Typically, referring to the computer-implemented aspects of thedisclosure, one or more of the method steps or even all of the methodsteps of the method according to one or more of the embodimentsdisclosed herein may be performed by using a computer or computernetwork. Thus, generally, any of the method steps including provisionand/or manipulation of data may be performed by using a computer orcomputer network. Generally, these method steps may include any of themethod steps, typically except for method steps requiring manual work,such as providing the samples and/or certain aspects of performing theactual measurements.

Specifically, the present disclosure further provides:

-   -   A computer or computer network comprising at least one        processor, wherein the processor is adapted to perform the        method according to one of the embodiments described in this        description,    -   a computer loadable data structure that is adapted to perform        the method according to one of the embodiments described in this        description while the data structure is being executed on a        computer,    -   a computer program, wherein the computer program is adapted to        perform the method according to one of the embodiments described        in this description while the program is being executed on a        computer,    -   a computer program comprising program means for performing the        method according to one of the embodiments described in this        description while the computer program is being executed on a        computer or on a computer network,    -   a computer program comprising program means according to the        preceding embodiment, wherein the program means are stored on a        storage medium readable to a computer,    -   a storage medium, wherein a data structure is stored on the        storage medium and wherein the data structure is adapted to        perform the method according to one of the embodiments described        in this description after having been loaded into a main and/or        working storage of a computer or of a computer network, and    -   a computer program product having program code means, wherein        the program code means can be stored or are stored on a storage        medium, for performing the method according to one of the        embodiments described in this description, if the program code        means are executed on a computer or on a computer network.

In a further embodiment of the present disclosure, an analytical devicefor determining a concentration of at least one analyte in bodily fluidis disclosed. The analytical device comprises:

-   -   at least one signal generator device adapted to generate at        least one excitation voltage signal, wherein the excitation        voltage signal comprises at least one poly frequent alternating        current (AC) voltage and at least one direct current (DC)        voltage profile, wherein the poly frequent AC voltage comprises        at least two frequencies;    -   at least one measurement unit, wherein the measurement unit is        adapted to receive a response,    -   at least one evaluation device adapted to evaluate an AC current        response for each frequency and a DC current response from the        response, wherein the evaluation device is adapted to evaluate        for each frequency at least one phase information and at least        one impedance information is evaluated from the AC current        response,

wherein the evaluation device is adapted to determine a concentration ofthe analyte from the DC current response and from one or both of thephase information and impedance information by using at least onepredetermined relationship.

For definitions of the features of the analytical device and foroptional details of the analytical device, reference may be made to oneor more of the embodiments of the method as disclosed above or asdisclosed in further detail below.

The term “measuring unit” generally may refer to an arbitrary device,typically an electronic device, which may be configured to detect atleast one signal, in particular the response. The measurement unit maybe adapted to receive a response at at least two different measurementtime points.

The signal generator may be adapted to apply the excitation voltagesignal to at least two measurement electrodes of at least one testelement. The analytical device may be handled independently from a testelement and may be adapted to interact with the test element in order toperform an analysis, such as by detecting the at least one response.Thus, the term “analytical device” may often also be referred to as ameasurement device, an analytical device, a meter or a test device.

The analytical device may be adapted to perform the method fordetermining a concentration of at least one analyte in bodily fluidaccording to one or more of the embodiments of the method according tothe present disclosure.

In a further embodiment of the present disclosure, a test elementanalysis system for determining a concentration of at least one analytein bodily fluid is provided. The test element analysis system comprises:

-   -   at least one analytical device according to one or more of the        embodiments of the analytical device according to the present        disclosure;    -   at least one test element having at least one measuring zone        capable of performing at least one change being characteristic        for the analyte, wherein the test element comprises at least two        measuring electrodes.

For definitions of the features of the test element analysis system andfor optional details of the test element analysis system, reference maybe made to one or more of the embodiments of the method and analyticaldevice as disclosed above or as disclosed in further detail below.Specifically, the test element analysis system may be embodied havingthe features referring to the analytical device according to one or moreof the embodiments of the analytical device.

As further used herein, the term “system” refers to an arbitrary set ofinteracting or interdependent component parts forming a whole.Specifically, the components may interact with each other in order tofulfill at least one common function. The at least two components may behandled independently or may be coupled or connectable. Thus, the term“test element analysis system” generally refers to a group of at leasttwo elements or components which are capable of interacting in order toperform at least one analytical detection by interacting with anarbitrary test element, specifically at least one analytical detectionof at least one analyte of the sample. The test element analysis systemmay generally also be referred to as an analytical system, an analyticalkit, a sensor system or a measurement system.

The term “test element” generally may refer to an arbitrary device whichis capable of detecting the analyte in the sample or of determining theparameter of the sample. The test element may specifically be astrip-shaped test element. As used herein, the term “strip-shaped”refers to an element having an elongated shape and a thickness, whereinan extension of the element in a lateral dimension exceeds the thicknessof the element, such as by at least a factor of 2, typically by at leasta factor of 5, more typically by at least a factor of 10, and mosttypically by at least a factor of 20 or even at least a factor of 30.Thus, the test element may also be referred to as test strip.

The test element may comprise at least one component or at least onereagent which changes at least one detectable property when the analyteis present in the sample such as a test chemistry. The term “testchemistry”, also referred to as a test chemical, may refer to anarbitrary material or a composition of materials adapted to change atleast one detectable property in the presence of the analyte. Generally,this property may be selected from an electrochemically detectableproperty and/or an optically detectable property, such as a color changeand/or a change in re-missive properties. Specifically, the testchemistry may be a highly selective test chemistry, which only changesthe property if the analyte is present in the sample of the body fluidapplied to the test element, whereas no change occurs if the analyte isnot present. More typically, the degree or change of the property may bedependent on the concentration of the analyte in the body fluid, inorder to allow for a quantitative detection of the analyte.

Specifically, the test element may comprise at least one reagentconfigured for activating a coagulation of components of the body fluid.The reagent may comprise reactive components of thromboplastin and apeptide substrate. Thus, in case the reagent is exposed to the sample,the thromboplastin may activate a clotting and thrombin may begenerated. Thrombin may cleave the peptide substrate and anelectrochemical signal may be generated. The electrochemical signal maybe evaluated with regard to a time of its occurrence. However, otherreagents and/or measurement principles may be feasible.

As used herein, the term “electrochemical detection” refers to adetection of an electrochemically detectable property of the analyte byelectrochemical means, such as an electrochemical detection reaction.Thus, for example, the electrochemical detection reaction may bedetected by comparing one or more electrode potentials, such as apotential of a working electrode with the potential of one or morefurther electrodes such as a counter electrode or a reference electrode.The detection may be analyte specific. The detection may be aqualitative and/or a quantitative detection.

The test element may have the at least one measuring zone capable ofperforming at least one change being characteristic for the analyte orthe parameter. As further used herein, the term “measuring zone” mayrefer to an arbitrary area or region of an object wherein an arbitrarymeasurement, specifically an analytical measurement, is conducted.Specifically, the test chemistry as described above may be locatedwithin the measuring zone, particularly on a surface of the measuringzone. The test element may be an electrochemical test element.

The term “electrochemical test element” may refer to an arbitrary testelement configured for conducting at least one electrochemicaldetection. As used herein, the term “electrochemical detection” refersto a detection of an electrochemically detectable property of at leastone arbitrary analyte, such as an electrochemical detection reaction.Thus, for example, the electrochemical detection reaction may bedetected by comparing one or more electrode potentials, such as anelectrostatic potential of a working electrode with the electrostaticpotential of one or more further electrodes such as a counter electrodeor a reference electrode. The detection may be analyte specific. Thedetection may be a qualitative and/or a quantitative detection.

The test element may comprise at least one capillary configured forreceiving the sample. The term “capillary” generally refers to anarbitrary small, elongate void volume such as a small tube. Generally,the capillary may comprise dimensions in the millimeter orsub-millimeter range. Commonly, a fluidic medium may migrate through thecapillary by capillary action, wherein the fluidic medium may flow innarrow spaces of the capillary without an assistance of external forceslike gravity due to intermolecular forces between the fluidic medium anda surface of the capillary facing the fluidic medium. For example, thetest element may have at least one face to face electrode configuration.The test element may have at least one capillary open at three sides.Facing electrode surfaces may be coated with an absorbent reagent layer,such that the sample is absorbed and spread via the reagent coating.Facing electrode surfaces may be conductively connected by using aliquid layer.

The analytical device may comprise a test element holder. The term “testelement holder” generally may refer to an arbitrary object which isconfigured to receive or to hold an arbitrary test element.Specifically, the test element may be positioned on a specific positionwithin the test element holder, such that a movement of the test elementin at least one direction may be suppressed, at least to a large extent.Thus, the measurement zone of the test element may be located in apredetermined position relative to the measuring unit. The test elementmay specifically be configured to be put reversibly into the testelement holder. Thus, the test element may be removable form the testelement holder without further ado. Still, other embodiments arefeasible. The test element may be at least partially received in thetest element holder. The term “being received” may generally refer to acondition of an object as being located or inserted fully or at leastpartially into a receptacle or into an opening of another element. Thus,a part of the object may be located outside of the other element.Exemplarily, the test element holder may comprise at least onereceptacle configured for receiving the test element. Thus, thereceptacle may be shaped complementarily to the test element. Therefore,the receptacle and the test element may be configured to establish aform-fit connection. The test element holder may comprise at least onecontact element which allows an electrical contact between the testelement and the test element holder.

The proposed method, analytical device and test element analysis systemprovide many advantages over known devices and methods. In particular,the proposed method, analytical device and test element analysis systemallow determination of concentration of the analyte in consideration ofinterference effects and production tolerances. By applying theexcitation voltage signal composed AC voltage having differentfrequencies and the DC voltage profile, it may be possible to get thebest possible performance, e.g., from a test strip based analyteconcentration or sample property measurement in a whole blood sample, byconsidering all relevant interference effects and strip productiontolerances. The phase information and/or at least one impedanceinformation of each frequency of the AC current response in combinationwith the DC current response may allow obtaining differentiableinformation of interference effects and production tolerances.

Summarizing the findings of the present disclosure, the followingembodiments are typical:

Embodiment 1

A method for determining a concentration of at least one analyte inbodily fluid, the method comprising the following steps:

-   -   at least one signal generation step, wherein at least one        excitation voltage signal is generated by at least one signal        generator device, wherein the excitation voltage signal        comprises at least one poly frequent alternating current (AC)        voltage and at least one direct current (DC) voltage profile,        wherein the poly frequent AC voltage comprises at least two        frequencies;    -   at least one signal application step, wherein the excitation        voltage signal is applied to at least two measurement        electrodes;    -   at least one measurement step, wherein a response is measured by        using the measurement electrodes;    -   at least one evaluation step, wherein an AC current response for        each frequency and a DC current response are evaluated from the        response by at least one evaluation device, and wherein for each        frequency at least one phase information and at least one        impedance information is evaluated from the AC current response        by the evaluation device;    -   at least one determination step, wherein the concentration of        the analyte is determined from the DC current response and from        one or both of the phase information and impedance information        by using at least one predetermined relationship.

Embodiment 2

The method according to the preceding embodiment, wherein the AC voltageand DC profile are superimposed to form the excitation voltage signal.

Embodiment 3

The method according to the preceding embodiment, wherein thepredetermined relationship isbG=Σ _(i=1) ^(n) a _(i)DC_(i) e ^(Σ) ^(m=1) ^(f) ^(bm) ^(i) ^(Ym) ^(i)^(+cm) ^(i) ^(Pm) ^(i) ,

wherein bG is the determined analyte concentration, i denotes the numberof measurement time points, wherein i, n, f and m are natural integernumbers, m denotes the number of frequencies, a_(i), b_(i), c_(i) areweighting coefficients, Y_(mj) are admittance values from AC response atdifferent frequencies at time points, P_(mj) are phase angle values fromAC response at different frequencies at time points and DC_(i) are DCresponse values at selected DC response time points.

Embodiment 4

The method according to embodiment 1, wherein the predeterminedrelationship is

${{bG} = {\sum\limits_{i = 1}^{n}{\sum\limits_{m = 1}^{f}\left( {\frac{a_{m\; i}D\; C_{i}}{Y_{{({imag})}m\; i}} + \frac{b_{m\; i}D\; C_{i}}{Y_{{({real})}m\; i}}} \right)}}},$

wherein bG is the determined analyte concentration, i denotes the numberof measurement time points, wherein i, n, f and m are natural integernumbers, m denotes the number of frequencies, a_(i) and b_(i) areweighting coefficients, Y_((imag)mi) and Y_((real)mi) are real andimaginary parts of admittance values from AC response at differentfrequencies at time points and DC_(i) are DC response values at selectedDC response time points.

Embodiment 5

The method according to the preceding embodiment, wherein thepredetermined relationship is,

${{bG} = {\overset{n}{\sum\limits_{\underset{i \neq j}{i,{j = 1}}}}\left( {\frac{a_{i}D\; C_{i}}{Y_{i}} + {b_{i}\left( {\frac{D\; C_{i}}{Y_{i}} \cdot \frac{D\; C_{j}}{Y_{j}}} \right)}} \right)}},$

wherein bG is the determined concentration of the analyte, i and jdenote the number of measurement time points, wherein i, j and n arenatural integer numbers, a_(i), b_(i) and c_(i) are weightingcoefficients, Y_(i), and Y_(j) are either real or imaginary parts ofadmittance values from AC response at different frequencies at timepoints i and j. DC_(i), DC_(j) are DC response values at selected DCresponse time points.

Embodiment 6

The method according to any one of the two preceding embodiments,wherein the predetermined relationship is,

${{bG} = {\overset{n}{\sum\limits_{\underset{i \neq j}{i,{j = 1}}}}{\overset{f}{\sum\limits_{\underset{m \neq l}{m,{l = 1}}}}\left( {\frac{a_{m\; i}D\; C_{i}}{Y_{{({imag})}m\; i}} + \frac{b_{m\; i}D\; C_{i}}{Y_{{({real})}m\; i}} + {c_{m\; i}\left( {\frac{D\; C_{i}}{Y_{{({imag})}{mj}}} \cdot \frac{D\; C_{j}}{Y_{{({real})}{li}}}} \right)}} \right)}}},$

wherein bG is the determined concentration of the analyte, i and jdenote the number of measurement time points, wherein i, j, n, f, m andl are natural integer numbers, m and l denote the number of frequencies,a_(i), b_(i) and c_(i) are weighting coefficients, Y_((imag)mi),Y_((real)mi) Y_((imag)mj) and Y_((real)mj) are real and imaginary partsof admittance values from AC response at different frequencies at timepoints i and j and DC_(i), DCj are DC response values at selected DCresponse time points.

Embodiment 7

The method according to any one of the preceding embodiments, whereinfor each frequency at least one real and imaginary part of admittance isevaluated from the AC current response by the evaluation device.

Embodiment 8

The method according to any one of the preceding embodiments, whereinthe method comprises determining a predetermined relationship betweenthe concentration of the analyte and the DC current response, the phaseinformation and impedance information.

Embodiment 9

The method according to any one of the preceding embodiments, wherein inthe determination step the concentration of the analyte is determined inconsideration of interference effects and production tolerances.

Embodiment 10

The method according to the preceding embodiment, wherein interferenceeffects are selected from the group consisting of ambient conditions, inparticular temperature and humidity; sample properties, in particularsample temperature, hematocrit level, protein level, and ionic strength.

Embodiment 11

The method according to any one of the preceding embodiments, whereinthe bodily fluid is whole blood.

Embodiment 12

The method according to any one of the preceding embodiments, whereinthe analyte is glucose.

Embodiment 13

The method according to any one of the preceding embodiments, whereinthe poly frequent AC voltage comprises at least three frequencies.

Embodiment 14

The method according to any one of the preceding embodiments, whereinthe AC voltage has a magnitude less than 30 mV rms.

Embodiment 15

The method according to any one of the preceding embodiments, whereinthe method further comprises at least one selection step, wherein in theselection step from the measurement time points at least one DC timepoint is selected, wherein the DC time point is a time point at whichthe DC response current is used in the determination step.

Embodiment 16

The method according to the preceding embodiment, wherein the DC timepoint fulfills certain quality conditions.

Embodiment 17

The method according to any one of the preceding embodiments, whereinthe DC voltage profile comprises a time profile.

Embodiment 18

The method according to any one of the preceding embodiments, wherein DCvoltage profile is selected from the group consisting of: a voltammetricvoltage profile; an amperometric voltage profile.

Embodiment 19

The method according to any one of the preceding embodiments, whereinthe excitation voltage signal is applied during at least one testsequence.

Embodiment 20

The method according to the preceding embodiment, wherein the methodcomprises at least one storage step, wherein in the storage step the DCcurrent response is stored for a suitable number of time points of thetest sequence.

Embodiment 21

The method according to any one of the preceding embodiments, whereinthe method comprises at least one calibration step.

Embodiment 22

The method according to the preceding embodiment, wherein the methodfurthermore comprises at least one lot calibration step, wherein themeasured response may be re-scaled

Embodiment 23

The method according to any one of the two preceding embodiments,wherein in the determination step the concentration of the analyte isdetermined by using information from the calibration step.

Embodiment 24

The method according to any one of the preceding embodiments, wherein inthe evaluation step the AC current response and the DC current responseare separated using at least one two-way analog electronic filter, whichsplits the signals between about 100 Hz and 500 Hz, wherein below 100 Hzthe response is analyzed as DC and above 500 Hz it is analyzed as AC.

Embodiment 25

The method according to any one of the preceding embodiments, whereinthe predetermined relationship is one or more of selected, determinedand verified by mathematical methods selected from the group consistingof multivariate analysis, neuronal nets, moving mesh, lasso method,boosted random forest and bootstrapping, on at least one training dataset.

Embodiment 26

The method according to any one of the preceding embodiments, whereinthe method comprises determining activation times.

Embodiment 27

The method according to any one of the preceding embodiments, whereinthe method comprises a temperature calibration, wherein the temperaturecalibration comprises determining if a temperature is, during themeasuring time, within allowed and/or predetermined limit.

Embodiment 28

The method according to any one of the preceding embodiments, whereinthe method comprises at least one fail safe step, wherein the fail safestep comprises determining if the analyte concentration is valid withinpredetermined limits.

Embodiment 29

The method according to any one of the preceding embodiments, whereinthe method comprises a sample application step, wherein a sample ofbodily fluid is brought in contact with the measurement electrodes.

Embodiment 30

A computer program including computer-executable instructions forperforming the method for determining a concentration of at least oneanalyte in bodily fluid according to any of the preceding embodimentswhen the program is executed on a computer or computer network.

Embodiment 31

A computer-readable medium having computer-executable instructions forperforming the method for determining a concentration of at least oneanalyte in bodily fluid according to any of the preceding embodiments,wherein the computing device is provided by a computer.

Embodiment 32

A computer program product with program code means stored on amachine-readable carrier, in order to perform the method for determininga concentration of at least one analyte in bodily fluid according to anyof the preceding embodiments, when the program is executed on a computeror computer network.

Embodiment 33

An analytical device for determining a concentration of at least oneanalyte in bodily fluid, the analytical device comprising:

-   -   at least one signal generator device adapted to generate at        least one excitation voltage signal, wherein the excitation        voltage signal comprises at least one poly frequent alternating        current (AC) voltage and at least one direct current (DC)        voltage profile, wherein the poly frequent AC voltage comprises        at least two frequencies;    -   at least one measurement unit, wherein the measurement unit is        adapted to receive a response,    -   at least one evaluation device adapted to evaluate an AC current        response for each frequency and a DC current response from the        response, wherein the evaluation device is adapted to evaluate        for each frequency at least one phase information and at least        one impedance information is evaluated from the AC current        response, wherein the evaluation device is adapted to determine        a concentration of the analyte from the DC current response and        from one or both of the phase information and impedance        information by using at least one predetermined relationship.

Embodiment 34

The analytical device according to the preceding embodiment, wherein thesignal generator is adapted to apply the excitation voltage signal to atleast two measurement electrodes of at least one test element.

Embodiment 35

The analytical device according to any one of the two precedingembodiments, wherein the analytical device is adapted to perform themethod for determining a concentration of at least one analyte in bodilyfluid according to any of the preceding embodiments referring to amethod.

Embodiment 36

A test element analysis system for determining a concentration of atleast one analyte in bodily fluid, comprising:

-   -   at least one analytical device according to any of the preceding        embodiments referring to an analytical device;    -   at least one test element having at least one measuring zone        capable of performing at least one change being characteristic        for the analyte, wherein the test element comprises at least two        measuring electrodes.

Embodiment 37

The test element analysis system according to the preceding embodiment,wherein the test element is an electrochemical test element.

Embodiment 38

The test element analysis system according to any one of the precedingembodiments referring to a test element analysis system, wherein thetest element comprises at least one capillary configured for receiving asample of bodily fluid.

Embodiment 39

The test element analysis system according to any one of the precedingembodiments referring to a test element analysis system, wherein theanalytical device comprises at least one test element holder forpositioning the test element.

In order that the embodiments of the present disclosure may be morereadily understood, reference is made to the following examples, whichare intended to illustrate the disclosure, but not limit the scopethereof.

In FIG. 1, a schematic overview of an exemplary embodiment of a methodfor determining a concentration of at least one analyte in bodily fluidis shown. The method comprises at least one signal generation step 110.In the signal generation step 110 at least one excitation voltage signalmay be generated by at least one signal generator device 112. Theexcitation voltage signal comprises at least one poly frequentalternating current (AC) voltage and at least one direct current (DC)voltage profile.

The poly frequent AC voltage comprises at least two frequencies. The ACvoltage may have a sine waveform. Other wave forms are feasible. Forexample, the AC voltage may comprise at least two AC sine waves havingdifferent frequencies. The AC voltage may comprise at least two AC sinewaves having different frequencies, wherein the two AC signals aresuperimposed. The poly frequent AC voltage may comprise three, four ormore frequencies. The frequencies may be in the range of 500 Hz to 20kHz. In FIG. 4 a schematic embodiment of a composition of the polyfrequent AC voltage is shown. The poly frequent AC voltage may comprisefour superimposed frequencies, for example, 1 kHz (denoted withreference number 114), 2 kHz (denoted with reference number 116), 10 kHz(denoted with reference number 118) and 20 kHz (denoted with referencenumber 120). The signal generator device 112 may comprise at least oneAC-voltage source 122 and at least one DC-voltage source 124. The signalgenerator device 112 may be adapted to generate the at least one polyfrequent AC voltage. For example, the signal generator 112 may beadapted to generate multiple AC voltage signals 114, 116, 118, 120 eachhaving different frequencies and to sum up the multiple AC signals. Thesummed signal is denoted with reference number 126 in FIG. 4. The ACvoltage, in particular the summed signal, may have a magnitude oramplitude such that no faradic current response is generated. Forexample, in the embodiment shown in FIG. 4, each of the AC voltagesignals 114, 116, 118, 120 may have a magnitude less or equal 10 mV rmsand the magnitude of the AC voltage 126 may be less than 30 mV rms.

The signal generator device 112 may be adapted to generate at least oneDC profile. The DC voltage profile may comprise a time profile. The DCvoltage may be changed and/or may be varied continuously or stepwiseduring a measurement time. For example, the DC voltage may comprise atleast one step sequence. For example, the DC voltage profile maycomprise at least two voltage steps. For example, the DC voltage profilemay comprise three, four or five voltage steps. Even more voltage stepsare feasible. The steps of the DC voltage profile may be selected toallow for a differentiation between an analytical reaction and variousinterference reactions. The DC voltage may have a rectangular waveform.Other waveforms are feasible. The DC voltage profile may be selectedfrom the group consisting of: a voltammetric voltage profile; anamperometric voltage profile.

The AC voltage and DC profile may be superimposed. The signal generatordevice 112 may be adapted to apply the AC voltage and DC profilesimultaneously to the bodily fluid. The signal generator device 112 maybe adapted to apply the excitation voltage signal comprisingsuperimposed poly frequent AC voltage and DC profile to the bodilyfluid. The signal generator device 112 may be part of the measurementelectronics and/or may be connected to the measurement electronics, forexample of at least one evaluation device 128. The signal generator 112may be part of the evaluation device 128 or may be designed as aseparate device.

The method further comprises at least one signal application step 130,wherein the excitation voltage signal is applied to at least twomeasurement electrodes 132. The method comprises at least onemeasurement step 134. In the measurement step 134 a response ismeasured. The response may be measured at at least two differentmeasurement time points by using the measurement electrodes 132. Themethod comprises at least one evaluation step 136, wherein an AC currentresponse for each frequency and a DC current response are evaluated fromthe response by at least one evaluation device 128, and wherein for eachfrequency at least one phase information and at least one impedanceinformation is evaluated from the AC current response by the evaluationdevice 128. The method comprises at least one determination step 138,wherein the concentration of the analyte is determined from the DCcurrent response and from one or both of the phase information andimpedance information by using at least one predetermined relationship.

In FIG. 2 an embodiment of test element analysis system 140 is depicted.The test element analysis system 140 comprises at least one analyticaldevice 142 and at least one test element 144 having at least onemeasuring zone 146 capable of performing at least one change beingcharacteristic for the analyte, wherein the test element 144 comprisesat least two measuring electrodes 132. The test element 144 may be atest strip. The test element 144 may comprise at least one sampleopening 148 for applying the bodily fluid. The analytical device maycomprise at least one test element holder 150. The test element 144 maybe inserted into the analytical device 142. The test element 144 maycomprise at least two electrical contacts 152 which are electricallyconnected to the at least two measuring electrodes 132. The analyticaldevice 142 may be adapted to electrically contact the test element 144,in particular by contacting the electrical contacts 152.

In FIG. 3 an exemplary embodiment of an analytical device 142 is highlyschematically shown. The analytical device 142 comprises the at leastone signal generator device 112 adapted to generate at least oneexcitation voltage signal, wherein the excitation voltage signalcomprises at least one poly frequent alternating current (AC) voltageand at least one direct current (DC) voltage profile, wherein the polyfrequent AC voltage comprises at least two frequencies. The analyticaldevice 142 comprises at least one measurement unit 154, wherein themeasurement unit 154 is adapted to receive a response, in particular atat least two different measurement time points. The analytical device142 comprises at least one evaluation device 128. The measurement unit145 may be part of the evaluation unit 128.

The evaluation device 128 is adapted to evaluate an AC current responsefor each frequency and a DC current response from the response. Theevaluation device 128 is adapted to evaluate for each frequency at leastone phase information and at least one impedance information from the ACcurrent response. The evaluation device 128 is adapted to determine fromthe DC current response and from one or both of the phase informationand impedance information a concentration of the analyte by using atleast one predetermined relationship.

FIG. 5 shows a development over time of an excitation voltage signalusing an amperometric voltage profile as DC profile and DC response. Themethod according to the present disclosure may be used to compensatebias caused by a high concentration of the interfering substanceascorbic acid onto a glucose measurement with a glucose test strip. Theascorbic acid may reduce a redox mediator in a detection reagent incompetition to a glucose dehydrogenase enzyme and glucose and may causea positive biased test result. In FIG. 5, the excitation voltage U_(ex)in mV versus time t in seconds is depicted. In solid lines theexcitation voltage signal is shown. The excitation signal comprises apoly frequent AC voltage, which is depicted magnified in box 156. InFIG. 5, the excitation voltage signal comprises three DC voltage stepsto allow for a differentiation between the analytical reaction andvarious interference reactions. The excitation voltage signal may beapplied between two measuring electrodes 132, where one electrode may becovered with a reagent to measure a glucose concentration and a secondelectrode covered with a silver/silver-chloride layer ascounter-reference electrode. For example, the test element 144 maycomprise two measurement electrodes 132 arranged as coplanar electrodes.

In addition, in FIG. 5, the response I in μA versus time is shown forthree samples for three levels of ascorbic acid with the same glucoseconcentration each: for 0 mg/dl ascorbic acid (shown as diamond), for 30mg/dl ascorbic acid (shown as square) and for 100 mg/dl ascorbic acid(shown as triangle). When comparing the response of the samplecontaining only glucose to a sample which contains glucose and ascorbicacid, the response time profile may be different because of differentreaction velocity of the competing reactions. For example, at early testtimes after a sample is dosed, e.g., within the first two seconds of themeasurement, the difference can be seen. The ascorbic acid as a typicalinterfering substance may cause a positive bias of the DC response. Atvery first part of the response signal, within the first two seconds, aslope may be different due to the different velocities of the redoxmediator reaction with the ascorbic acid and the reaction with theglucose enzyme system. In the following, DC response determined duringthe very first part of the response signal will be denoted at early DCtime points. At a later time point, when the reactions are nearlyfinished, no differentiation may be possible. In the following, DCresponse determined during later time points of the response signal willbe denoted at later DC time points. FIG. 6 shows, for the samples shownin FIG. 5, development over time of the slopes dI/dt in μA/s of the DCresponses. The determination of the analyte concentration may compriseweighting the early DC time points and the later DC time points by usingthe predetermined relationship such that the ascorbic acid interferencecan be compensated.

When hematocrit levels of the blood sample or the ambient temperatureare different or when the strips are aged, compared to the example shownin FIGS. 5 and 6, relation of the reaction velocities and magnitude ofthe DC responses may change. Such interference effects may becompensated by determining for each of the DC time points thecorresponding results from the poly frequent impedance measurement atthe same time point. The analyte concentration is determined from the DCcurrent response and from one or both of the phase information andimpedance information by using the predetermined relationship. To eachobserved DC response time point the AC current response from thesimultaneous four-frequent AC excitation may be determined as fouradmittances and four phase angles.

For test elements having a coplanar electrode arrangement thepredetermined relationship may bebG=Σ _(i=1) ^(n) a _(i) DC _(i) e ^(Σ) ^(m=1) ^(f) ^(bm) ^(i) ^(Ym) ^(i)^(+cm) ^(i) ^(Pm) ^(i) ,

wherein bG is the determined analyte concentration, i denotes the numberof measurement time points, wherein i, n, f and m are natural integernumbers, m denotes the number of frequencies, a_(i), b_(i), c_(i) areweighting coefficients, Ym_(i) are admittance values from AC response atdifferent frequencies at time points, Pm_(i) are phase angle values fromAC response at different frequencies at time points and DC_(i) are DCresponse values at selected DC response time points.

The electrodes also can be arranged in a face to face configuration,where the active electrode surface is defined by isolating surroundinglayers. The test element may have a capillary to transport a liquidsample and defining a measuring cell. To detect a sufficient fill leveloften separate electrodes following the measuring electrodes along thecapillary channel are implemented to verify complete measuring electrodecoverage. In case of unstructured face to face electrodes, activeelectrode surfaces may depend on a sample fill level. This effect can becompensated by using a specific predetermined relationship. For example,for test elements having a face to face electrode arrangement thepredetermined relationship may be

${{bG} = {\sum\limits_{i = 1}^{n}{\sum\limits_{m = 1}^{f}\left( {\frac{a_{m\; i}D\; C_{i}}{Y_{{({imag})}m\; i}} + \frac{b_{m\; i}D\; C_{i}}{Y_{{({real})}m\; i}}} \right)}}},$

wherein bG is the determined analyte concentration, i denotes the numberof measurement time points, wherein i, n, f and m are natural integernumbers, m denotes the number of frequencies, a_(i) and b_(i) areweighting coefficients, Y_((imag)mi) and Y_((real)mi) are real andimaginary parts of admittance values from AC response at differentfrequencies at time points and DC_(i) are DC response values at selectedDC response time points. In particular, the predetermined relationshipmay be,

${{bG} = {\sum\limits_{\underset{i \neq j}{i,{j = 1}}}^{n}\left( {\frac{a_{i}D\; C_{i}}{Y_{i}} + {b_{i}\left( {\frac{D\; C_{i}}{Y_{i}} \cdot \frac{D\; C_{j}}{Y_{j}}} \right)}} \right)}},$

wherein bG is the determined concentration of the analyte, i and jdenote the number of measurement time points, wherein i, j and n arenatural integer numbers, a_(i), b_(i) and c_(i) are weightingcoefficients, Y_(i), and Y_(j) are either real or imaginary parts ofadmittance values from AC response at different frequencies at timepoints i and j. DC_(i), DC_(j) are DC response values at selected DCresponse time points.

In one embodiment, the predetermined relationship may be

${{bG} = {\overset{n}{\sum\limits_{\underset{i \neq j}{i,{j = 1}}}}{\sum\limits_{\underset{m \neq l}{m,{l = 1}}}^{f}\left( {\frac{a_{m\; i}D\; C_{i}}{Y_{{({imag})}m\; i}} + \frac{b_{m\; i}D\; C_{i}}{Y_{{({real})}m\; i}} + {c_{m\; i}\left( {\frac{D\; C_{i}}{Y_{{({imag})}m\; j}} \cdot \frac{D\; C_{j}}{Y_{{({real})}{li}}}} \right)}} \right)}}},$

wherein bG is the determined concentration of the analyte, i and jdenote the number of measurement time points, wherein i, j, n, f, m andl are natural integer numbers, m and l denote the number of frequencies,a_(i), b_(i) and c_(i) are weighting coefficients, Y_((imag)mi),Y_((real)mi) Y_((imag)mj) and Y_((real)mj) are real and imaginary partsof admittance values from AC response at different frequencies at timepoints i and j, and DC_(i), DCj are DC response values at selected DCresponse time points. This predetermined relationship may be used fortest elements having face to face electrodes.

The method further may comprise at least one selection step, wherein inthe selection step from the measurement time points at least one DC timepoint is selected. In the selection step from the measurement timepoints a number of DC time points may be selected. For example, three,four, five, six, ten or even twelve DC time points may be selectedduring at least one test sequence and/or during at least one voltagestep of the excitation voltage signal during the test sequence. Even ahigher number of DC time points may be feasible. The DC time point maybe a time point at which the DC response current is used in thedetermination step. The DC time point may fulfill certain qualityconditions, such as good correlation with the reference glucose valuesand with the various interference effects. FIG. 7 shows an example ofthe selection of DC time points for the 100 mg/dl ascorbic acid sample(shown as triangle) and excitation profile as described with respect toFIG. 5. In FIG. 7, twelve DC time points are selected, denoted as DC1 toDC12. For each DC voltage step four DC time points are selected, whereintwo DC time points are selected at the beginning of each DC voltage stepand two DC time points are selected at later time points during each DCvoltage step. For each of the selected DC time points the DC_(i)response value may be determined and or stored. At the same time point,i.e., the DC time point, the AC response value may be determined foreach of the superimposed frequencies. The analyte concentration may bedetermined and/or calculated from the DC response values and thesimultaneously determined AC response values by using the abovedescribed predetermined relationship with significantly reduced impactof interference effects.

The evaluation device 128 may be adapted to determine the predeterminedrelationship. The evaluation device 128 may be adapted to providemathematical functions and weighting coefficients which, for example,may be stored in a data storage and/or look-up table of the evaluationdevice 128. The method may comprise at least one training step, whereinthe predetermined relationship may be determined. The predeterminedrelationship, in particular weighting coefficients of the predeterminedrelationship, may be one or more of selected, determined and verified bymathematical methods selected from the group consisting of multivariateanalysis, neuronal nets, moving mesh, lasso method, boosted randomforest and bootstrapping, on at least one training data set. Thetraining data set may be collected by performing co-variance studies.The training data set may comprise a suitable number of repeatedmeasurements, for example with homogenous produced test elements, byapplying a selected test sequence with connected electronic circuitry ofa measurement device, for example a meter. To obtain the training dataset the analyte concentration of each test sample may be determined witha reference method, for example hexokinase method in case of a glucoseconcentration. To obtain the training data set each combination ofrelevant combined interference effects may be tested across a relevantconcentration range of the analyte with a sufficient amount ofrepetition for each test combination and test sample. For example, inthe case of determining a glucose concentration in a blood sample themajor interference effects may be ambient temperatures, hematocritlevel, ionic strength, plasma concentrations, lipid concentration oradministered interfering substances, especially antioxidants. In case oftest elements with unstructured face to face electrodes, which may notcomprise separate fill sufficient detection electrodes, a fill level ofa capillary may be tested for the training data set generation. Anotherinterference effect might be the storage time in a primary test elementpackage or an impact of environmental condition and exposer time of atest element, e.g., a test strip, when the test element is taken out ofthe package before executing the measurement. If the test element is notsufficiently robust versus these impacts, also these factors may beconsidered when obtaining the training data set.

The predetermined relationship, in particular weighting coefficients,may be determined to get a concentration measurement result with therequired performance. For the example of a determination of a glucoseconcentration, that means that the concentration of more than 95% of themeasurements does not differ more than +/−10%, or 10 mg/dl, from theused reference method, when tested with all relevant sample material andtest conditions. For example, a moving mesh method with randomoscillating step size may be used to determine the weightingcoefficient. The training step may comprise an optimization, wherein aminimum of an objective function is determined. As objective function anormalized error to the reference method equivalent to an MSD (meansquare deviation) may be used:objective function=Average[Σ_(i=1) ^(n)NE_(i)]²,

wherein NE_(i) is the normalized error:NE_(i) =bG _(i) −Gref_(i), for Gref_(i)<100 mg/dl, orNE_(i)=(bG _(i) −Gref_(i))/Gref_(i)·100, for Gref_(i)>100 mg/dl,

wherein bG_(i) is the determined glucose concentration and Gref_(i) isthe glucose reference value.

FIG. 8 shows experimental results for a face to face electrode testelement with a glucose enzyme-redox-mediator reagent on a gold surfaceas working electrode and a silver/silver-chloridecounter-reference-electrode. The normalized error of the calculatedglucose result versus the reference method is shown. For the experiment,blood samples of three glucose levels, each adjusted to hematocritlevels of 0, to 70%, are tested at ambient temperatures of 12, 23 and40° C. Results are also included for blood samples spiked with a highconcentration of up to 100 mg/dl ascorbic acid at the three glucoselevels. Amperometric DC measurements, without using AC information, aredepicted with crosses. Normalized errors for analyte concentrationsusing the method according to the present disclosure, e.g., usingresponse of simultaneous poly frequent AC and three step DC, aredepicted as diamonds and are 100% within a range of +/−5% or mg/dl forthe shown training data set.

FIGS. 9 and 10 show an example of an excitation voltage signal U_(ex) inmV versus time using a combination of a cyclic voltammetry superimposedwith DC pulses and additionally superimposed with a poly frequent ACvoltage. FIG. 9 shows the DC profile using cyclic voltammetry. The DCvoltage has a rectangular wave form. A base voltage or start value at 0mV is shown. The DC voltage profile may comprise increasing, e.g., insteps, the DC voltage from a start value to a first turning point,subsequent decreasing from the first turning point to a second turningpoint and subsequent increasing from the second turning point to thestart value. FIG. 10 shows the excitation voltage signal comprising DCvoltage profile and poly frequent AC voltage. A region (circle) of theexcitation voltage signal is enlarged, in order to visualize thecomposition of the excitation voltage signal. In the big box the polyfrequent AC voltage is shown. In the big circle with dashed lines, theexcitation voltage signal is depicted as a solid line. Superimposed, forreference, the corresponding response, i.e., current response, is shownas a dashed line. DC_(i) values may be selected from the end of the highpulse and low pulse phase from each rectangular DC pulse, where the basevoltage is increased in steps to a first turning point, going down to asecond turning point and going back to the start voltage. A voltagechange range and direction may be adjusted to the used redox mediatorsand relevant redox active interfering substances, which can occur in atest sample. Usually for test strip based systems, during test time themeasurement zone, also denoted as reaction zone, is not in a steadystate situation due to dissolved reagent layer, sample temperaturegradients and/or dosing effects. These effects can be compensated byusing the information from the poly frequent AC response in combinationwith the related DC response. From each rectangular DC pulse,superimposed with the poly frequent AC excitation, two DC_(i) values andthe related admittance and phase values from the superimposedfrequencies may be selected.

For the example shown in FIGS. 9 and 10, the above describedpredetermined relationship may be used to determine the analyticalresult, i.e., the analyte concentration. Weighting coefficients may bedetermined using a moving mesh method. Alternatively, neuronal net ormultivariate regression methods or combinations of these methods may beused. Other mathematical methods (e.g., the lasso method) may be used toidentify and select the relevant observables and to reduce their totalnumber in order to reduce the complexity of the determination andimprove portability of the found predetermined relationship from theused training data on independently collected verification data sets.

In FIGS. 11 to 13 experimental results for a glucose test strip for theexcitation signal of FIGS. 9 and 10 is shown. The test elements may havea capillary to receive a test sample and structured gold electrodes onthe bottom of the capillary, which are both covered with the same drieddetection reagent. The electrodes may be identical and the detectionreagent may support anodic and cathodic electrode reaction. Counter andworking electrode may be defined by polarity generating the analyticalreaction on one of the electrodes. FIG. 11 shows the normalized error NEof the determined analyte concentration, i.e., the glucose value, versusthe reference method. All relevant test conditions and sample types areincluded in the training data set used to derive the coefficient for thegiven algorithm model. It is found that more than 99% of the NEs arewithin +/−8% (mg/dl) for the training data set. FIG. 12 shows thenormalized errors for using poly frequent AC and DC profile informationsimultaneously (diamonds) compared to using a DC response of anamperometric measurement (crosses) for the determination of the analyteconcentration. The determination using a DC response of an amperometricmeasurement only exhibits a larger scattering behavior compared to thedetermination using poly frequent AC and DC profile informationsimultaneously. For the shown data the manipulated blood samples withhematocrit levels from 0 to 70%, sodium levels from 110 to 190 mmol/l,potassium bromide concentrations up to 450 mg/ml and ascorbic acid andglutathione levels up to 100 mg/dl are used at ambient temperaturesbetween 12 to 40° C. The test elements were tested immediately afterbeing taken from protective packaging and with up to 96 hours' exposuretime at tropical ambient conditions. The training data set includes allkind of combinations of the above described test conditions and sampletypes.

FIG. 13 shows the normalized error for a verification data set. Theverification data set comprises measurement data, which was not used forweighting coefficient derivation. For FIG. 13, the predeterminedrelationship, in particular the mathematical model and weightingcoefficients, determined with the training data set is used on theverification data set to determine the analyte concentration. Still morethan 96% of the normalized errors are within +/−8% (mg/dl).

LIST OF REFERENCE NUMBERS

-   110 signal generation step-   112 signal generator device-   114 AC voltage signal-   116 AC voltage signal-   118 AC voltage signal-   120 AC voltage signal-   122 AC-voltage source-   124 DC-voltage source-   126 AC voltage-   128 evaluation device-   130 signal application step-   132 measurement electrodes-   134 measurement step-   136 evaluation step-   138 determination step-   140 test element analysis system-   142 analytical device-   144 test element-   146 measuring zone-   148 sample opening-   150 test element holder-   152 electrical contacts-   154 measurement unit-   156 box

What is claimed is:
 1. A method for determining a concentration of atleast one analyte in bodily fluid, the method comprising the followingsteps: at least one signal generation step, wherein at least oneexcitation voltage signal is generated by at least one signal generatordevice, wherein the excitation voltage signal comprises at least onepoly frequent alternating current (AC) voltage and at least one directcurrent (DC) voltage profile, wherein the poly frequent AC voltagecomprises at least two frequencies; at least one signal applicationstep, wherein the excitation voltage signal is applied to at least twomeasurement electrodes, which are in contact with the bodily fluid andwhich are adapted to determine the analyte electrically orelectrochemically; at least one measurement step, wherein a response ismeasured by using the measurement electrodes; at least one evaluationstep, wherein an AC current response for each frequency and a DC currentresponse are evaluated from the response by at least one evaluationdevice, and wherein for each frequency at least one phase informationand at least one impedance information is evaluated from the AC currentresponse by the evaluation device; at least one determination step,wherein the concentration of the analyte is determined from the DCcurrent response and from one or both of the phase information andimpedance information by using at least one predetermined relationship,wherein the AC voltage and DC profile are superimposed to form theexcitation voltage signal, and determining a predetermined relationshipbetween the concentration of the analyte and the DC current response,the phase information and impedance information.
 2. The method accordingto claim 1, wherein the predetermined relationship is $\begin{matrix}{{{bG} = {\sum\limits_{i = 1}^{n}{a_{i}{DC}_{i}e^{{\Sigma_{m = 1}^{f}{bm}_{i}{Ym}_{i}} + {c\; m_{i}{Pm}_{i}}}}}},} & \;\end{matrix}$ wherein bG is the determined analyte concentration, idenotes the number of measurement time points, wherein i, n, f and m arenatural integer numbers, m denotes the number of frequencies, a_(i),b_(i), c_(i) are weighting coefficients, Ym_(j) are admittance valuesfrom AC response at different frequencies at time points, Pm_(j) arephase angle values from AC response at different frequencies at timepoints and DC_(i) are DC response values at selected DC response timepoints.
 3. The method according to claim 1, wherein the predeterminedrelationship is${{bG} = {\sum\limits_{i = 1}^{n}{\sum\limits_{m = 1}^{f}\left( {\frac{a_{m\; i}D\; C_{i}}{Y_{{({imag})}m\; i}} + \frac{b_{m\; i}D\; C_{i}}{Y_{{({real})}m\; i}}} \right)}}},$wherein bG is the determined analyte concentration, i denotes the numberof measurement time points, wherein i, n, f and m are natural integernumbers, m denotes the number of frequencies, a_(i) are weightingcoefficients, Y_((imag)mi) and Y_((real)mi) are real and imaginary partsof admittance values from AC response at different frequencies at timepoints and DC_(i) are DC response values at selected DC response timepoints.
 4. The method according to claim 3, wherein the predeterminedrelationship is,${{bG} = {\sum\limits_{\underset{i \neq j}{i,{j = 1}}}^{n}\left( {\frac{a_{i}\; D\; C_{i}}{Y_{i}} + {b_{i}\left( {\frac{D\; C_{i}}{Y_{i}} \cdot \frac{D\; C_{j}}{Y_{j}}} \right)}} \right)}},$wherein bG is the determined concentration of the analyte, i and jdenote the number of measurement time points, wherein i, j and n arenatural integer numbers, a_(i), b_(i) and c_(i) are weightingcoefficients, Y_(i), and Y_(j) are either real or imaginary parts ofadmittance values from AC response at different frequencies at timepoints i and j, DC_(i), DC_(j) are DC response values at selected DCresponse time points.
 5. The method according to claim 3, wherein thepredetermined relationship is${{bG} = {\sum\limits_{\underset{i \neq j}{i,{j = 1}}}^{n}{\sum\limits_{\underset{m \neq l}{m,{l = 1}}}^{f}\left( {\frac{a_{m\; i}D\; C_{i}}{Y_{{({imag})}m\; i}} + \frac{b_{m\; i}D\; C_{i}}{Y_{{({real})}m\; i}} + {c_{m\; i}\left( {\frac{D\; C_{i}}{Y_{{({imag})}m\; j}} \cdot \frac{D\; C_{j}}{Y_{{({real})}{li}}}} \right)}} \right)}}},$wherein bG is the determined concentration of the analyte, i and jdenote the number of measurement time points, wherein i, j, n, f, m andl are natural integer numbers, m and l denote the number of frequencies,a_(i), b_(i) and c_(i) are weighting coefficients, Y_((imag)mi),Y_((real)mi) Y_((imag)mj) and Y_((real)mj) are real and imaginary partsof admittance values from AC response at different frequencies at timepoints i and j, and DC_(i), DCj are DC response values at selected DCresponse time points.
 6. The method according to claim 1, wherein in thedetermination step the concentration of the analyte is determined inconsideration of interference effects and production tolerances.
 7. Themethod according to claim 1, wherein the AC voltage has a magnitude lessthan 30 mV rms.
 8. The method according to claim 1, wherein the methodfurther comprises at least one selection step, wherein in the selectionstep from the measurement time points at least one DC time point isselected, wherein the DC time point is a time point at which the DCresponse current is used in the determination step.
 9. The methodaccording to claim 1, wherein the DC voltage profile comprises a timeprofile, wherein DC voltage profile is selected from the groupconsisting of: a voltammetric voltage profile; an amperometric voltageprofile.
 10. The method according to claim 1, wherein in the evaluationstep the AC current response and the DC current response are separatedusing at least one two-way analog electronic filter, which splits thesignals between about 100 Hz and 500 Hz, wherein below 100 Hz theresponse is analyzed as DC and above 500 Hz it is analyzed as AC. 11.The method according to claim 1, wherein the predetermined relationshipis one or more of selected, determined and verified by mathematicalmethods selected from the group consisting of multivariate analysis,multilinear principal component analysis, neuronal nets, moving mesh,lasso method, boosted random forest and bootstrapping, on at least onetraining data set.
 12. The method according to claim 1, wherein themethod comprises at least one fail safe step, wherein the fail safe stepcomprises determining if the analyte concentration is valid withinpredetermined limits.
 13. The method according to claim 1, wherein themethod comprises a sample application step, wherein a sample of bodilyfluid is brought in contact with the measurement electrodes.